The goal of this research is to develop a mouse wound healing model to resolve a fundamental controversy concerning the role of differentiated keratinocytes in wound repair and determine functional plasticity of differentiated keratinocytes in wound conditions. An inducible bigenic mouse will be created to serve as a keratinocyte lineage model to test the roles of suprabasal and basal keratinocytes in epidermal wound healing. This R21 application will test the hypothesis that suprabasal keratinocytes, in response to wounding, actively participate in epithelial repair and maintain cellular plasticity. Strategies to promote wound closure in chronic wounds must be focused on a cell population capable, by virtue of numbers, location and functionality, to effect wound reepithelialization. This hypothesis will be tested with the following Specific Aims: 1) Refine a bigenic mouse model in which enhanced yellow fluorescent protein is expressed exclusively in differentiated suprabasal keratinocytes, and 2) Use the bigenic mouse to determine specific roles of suprabasal and basal keratinocytes in epidermal migration during wound healing. Relevance: This bigenic mouse model, in addition to resolving a long-standing controversy of the role of suprabasal keratinocytes in epidermal wound closure, will be useful for studies of: 1) chronic wounds in which there is a reduction of epidermal migration, but an increase in epidermal proliferation, 2) differentiated keratinocyte plasticity, 3) diseases in which suprabasal genes are mutated, such as epidermolytic hyperkeratosis and loricrin keratoderma, and 4) cutaneous integration into porous percutaneous devices where the biomaterial/skin interface has been engineered to promote epithelial ingrowth/attachment to medical devices. PUBLIC HEALTH RELEVANCE: Through this research project we will create a mouse keratinocyte lineage model with which we will be able to identify cells actively involved in skin wound healing. Targeting these cells for therapy is critical in non-healing chronic wounds, for the study of skin diseases, and for studies that promote epithelial in growth/attachment to medical devices.